Guidewires are commonly used in conjunction with intravascular devices, for example intravascular catheters or other such devices, to facilitate navigation through the vasculature of a patient. The vasculature of a patient may be very tortuous. It is often desired that certain portions of a guidewire have lateral flexibility characteristics as well as pushability characteristics. It is also desirable that the guidewire be able to achieve a rigid state from a flexible state, to achieve a shape-locked configuration, and to revert to a flexible state from the rigid state.